(1) Field of the Invention
The present invention relates to an electrode apparatus for the dialysis, which can easily remove unnecessary ionic substances from a solution in electrodeposition coating, electroplating or the like. More particularly, the present invention relates to an electrode apparatus for the dialysis, valuably usable in electrodeposition coating, in which a counter electrode for the electrode of a material to be coated is separated from a solution through a tubular ion exchanger.
(2) Description of the Related Art
Electrodeposition coating is roughly divided into the anion type coating and cation type coating. An anionic paint or cationic paint composed mainly of a resin is used in the form of an aqueous solution, and an alkali or acid is added to the solution to adjust the electroconductivity of the solution. Accordingly, in carrying out electrodeposition coating, the paint solution is supplied with decrease of the paint component, and therefore, the alkali or acid in the solution is gradually accumulated to cause changes of the electroconductivity and other conditions, with the result that bad influences are imposed on smooth formation of a uniform coating. Accordingly, in order to eliminate this disadvantage, there is generally adopted a control method in which a counter electrode for the electrode of a material to be coated is separated from a solution through an ion exchange membrane and the alkali or acid is dialyzed and removed from the solution through the membrane.
In this electrodeposition coating, as the electrode separated by an ion-exchange membrane, there has been used an electrode unit apparatus dismountable from a solution, which comprises a box-type hollow vessel having an electrode disposed therein with an ion-exchange membrane as the barrier, as disclosed in Japanese Examined Patent Publication (Kokoku) No. 45-22231. In this membrane electrode apparatus of the box type comprising an ion-exchange membrane, however, even though the membrane is supported by a non-conductive net or porous structure, by the change of the hydraulic pressure of the solution caused by feeding and withdrawal of a material to be coated, the membrane is inevitably deformed and the membrane fails to maintain a good durability for a long time, and there is a risk of breaking of the membrane. Therefore, the membrane should be periodically exchanged with a fresh membrane, and because of weight of the apparatus, this exchange operation is not easy, with the result that the efficiency of the electrodeposition coating is reduced and the running cost increases.
As the means for overcoming this disadvantage, Japanese Examined Patent Publication (Kokoku) No. 57-27955 proposes a membrane electrode apparatus for the electrodeposition coating, in which it is intended to improve the durability of an ion-exchange membrane, increase the electrodeposition coating efficiency and reduce the size and weight of the apparatus. The diaphragm electrode apparatus for the electrodeposition coating, disclosed in Japanese Examined Patent Publication (Kokoku) No. 57-27955, is constructed so that an ion-exchange membrane is laminated on the surface of an electrode through a supporting member having a liquid-circulating mechanism to support the ion-exchange membrane with a good durability, and water is forcibly circulated from the outside through the supporting member to remove air bubbles adhering to the electrode and polarized molecules of impurities. More specifically, a cylindrical membrane electrode apparatus for the electrodeposition coating, which comprises an ion-exchange membrane wound and laminated on the periphery of a tubular electrode through a network spacer, is disclosed. In the barrier membrane electrode apparatus for the electrodeposition coating, proposed in Japanese Examined Patent Publication (Kokoku) No. 57-27955, since it is indispensable that the ion-exchange membrane should be laminated on the surface of the electrode through the supporting member, the troublesome operation of winding, laminating and bonding the ion-exchange membrane should be performed. Furthermore, in this ion-exchange membrane, a seam is inevitably formed on the side face, leaking of the electrodeposition coating liquid into the electrode compartment or leaking of the electrolyte into the tank of electrodeposition coating liquid is often caused.
In general, the ion-exchange membrane elongates in the electrodeposition coating liquid, and the ion-exchange membrane contracts when it is taken out from the electrodeposition coating liquid. In the above-mentioned barrier membrane electrode apparatus for the electrodeposition coating, since the ion-exchange membrane is fixed together with the membrane-supporting member to the electrode, the elongation and contraction of the ion-exchange membrane are not absorbed, and therefore, wrinkling is readily caused and there is a risk of breaking of the ion-exchange membrane.